When building mypackage, everything seems to work:
library(devtools)
build(vignettes = T, manual = T)
* checking for file ‘/storage/Documents/client/validate/my
I don't know for the manual, but if you build from rstudio using the 'build and reload' button (nearby the check buttonl, the vignettes, if properly built, should end up in 'yourpackage' subfolder of your r library folder, i think in inst/doc sub sub folder.
Also, for vignettes did you try building them using devtools::build_vignettes
? Usually works for me.